Oral formulations are required to pass a test satisfying a dissolution test standard, such as a dissolution test described in non-patent document 1. This dissolution test is performed using prescribed vessels. In doing so, the vessel is placed on a thermostatic water bath having suitable size or a thermostatic jacket, and is warmed.
Conventionally, testing machines with the thermostatic water bath have been often used. In late years, however, the testing machines with the thermostatic jacket are used from a viewpoint of the simplicity of a test operation, higher efficiency and the like (non-patent document 1).